The present invention relates to improvements in locking devices particularly for doors. The invention is especially directed to door locking devices of the type which include a plurality of locking bars projectable from all four sides of a door into recesses in the door frame, and is therefore described below with respect to this application.
A number of such door locking devices are now in use. As a rule, however, the known devices have a limited movement of the locking bars from their withdrawn unlocking positions to their projected locking positions, which limited movement affects the locking strength of the bars when in their locking positions. In addition, in the known devices the force applied to the locking bars, in case of an attempted forced entry, is usually taken-up by relatively weak structural elements, such as pins. Thus, the known locking devices of this type generally can withstand only a force of up to about 400 Kgm if a forced entry is attempted.